Sensor system for tire

ABSTRACT

A sensor system for a tire, which enables the installation condition of a sensor unit in a tire&#39;s air chamber to be know. A sensor system where a sensor unit is installed in a tire&#39;s air chamber has detecting means for detecting a relative change in the distance between the sensor unit and a position where the sensor unit is installed.

TECHNICAL FIELD

The present invention relates to a sensor system for a tire, whichdetects information inside the tire such as an air pressure and atemperature, and more particularly relates to a sensor system for a tirewhich enables an installation condition of a sensor unit in a tire's airchamber to be known.

BACKGROUND ART

In order to monitor information inside a tire, such as an air pressureand a temperature, there has been heretofore performed attachment of asensor unit to an inner surface of the tire, a well part of a rim or thelike, detection of the information inside the tire by use of the sensorunit, and transmission of the detection results to a receiver outsidethe tire by utilizing radio waves (for example, see Japanese patentapplication Kohyo publication No. Hei 10(1998)-504783).

In such a sensor system for a tire, a sensor unit is installed in atire's air chamber. Thus, there is a drawback that, even if the sensorunit falls off a predetermined installation position in assembly of arim, the falling of the sensor unit cannot be known. If a vehicle runswhile the sensor unit has fallen off, an electronic component of thesensor unit will be destroyed, and communication may be disabled or afalse alarm may be given.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a sensor system fora tire which enables an installation condition of a sensor unit in atire's air chamber to be known.

A sensor system for a tire of the present invention to achieve theforegoing object is a sensor system for a tire, in which a sensor unitis installed in a tire's air chamber, including detecting means fordetecting a relative change in a distance between the sensor unit and aposition where the sensor unit should be installed.

As described above, by providing the detecting means for detecting therelative change in the distance between the sensor unit and the positionwhere the sensor unit should be installed, if the sensor unit falls offa predetermined installation position in assembly of a rim, the fallingof the sensor unit can be easily known. Therefore, destruction of anelectronic component, disabled communication, a false alarm, and thelike attributable to the falling of the sensor unit can be prevented.

In the present invention, in order to detect the relative change in thedistance between the sensor unit and its installation position, thefollowing structure can be adopted.

Specifically, a sensor system for a tire of the present invention is asensor system for a tire, in which a sensor unit is installed in atire's air chamber, including: a base which fixes the sensor unit in itsinstallation position, the base being attached to the sensor unit; aconductive path with a pair of contact points formed in the base, theconductive path connecting the contact points thereof; and a detectioncircuit with a pair of contact points formed in the sensor unit, thedetection circuit connecting the contact points thereof, and the contactpoints being arranged corresponding to positions of the contact pointsin the base. In the system, a relative change in a distance between thesensor unit and its installation position is detected based on an openand closed state of the detection circuit.

Moreover, a sensor system for a tire of the present invention is asensor system for a tire, in which a sensor unit is installed in atire's air chamber, including a proximity sensor which reacts to metal,the proximity sensor being arranged in the sensor unit. In the system, arelative change in a distance between the sensor unit and itsinstallation position is detected based on an output of the proximitysensor.

Furthermore, a sensor system for a tire of the present invention is asensor system for a tire, in which a sensor unit is installed in atire's air chamber, including, a probing member which is elasticallyenergized toward an installation position of the sensor unit, theprobing member being arranged in the sensor unit. In the system, arelative change in a distance between the sensor unit and itsinstallation position is detected based on displacement of the probingmember.

Furthermore, a sensor system for a tire of the present invention is asensor system for a tire, in which a sensor unit is installed in atire's air chamber, including a passive transponder mounted in thesensor unit. In the system, a relative change in a distance between thesensor unit and its installation position is detected based on aresponse of the passive transponder to a reader having a limited output.

In the present invention, the sensor unit includes an electroniccomponent required to detect information inside the tire, the componentbeing housed in a case. The electronic component which constitutes thesensor unit, and structure of the case, are not particularly limited.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically showing a sensor systemfor a tire according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing a sensor systemfor a tire according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view schematically showing a sensor systemfor a tire according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view schematically showing a sensor systemfor a tire according to a fourth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the accompanying drawings, a configuration of thepresent invention will be described in detail below.

FIG. 1 shows a sensor system for a tire according to a first embodimentof the present invention. In FIG. 1, R denotes a rim, T denotes a tire,and S denotes a tire's air chamber. The sensor system for a tire of thisembodiment includes a sensor unit 1 for detecting information inside thetire, and a base 11 for fixing the sensor unit 1. The sensor unit 1 isinstalled in the tire's air chamber by means of the base 11.

The sensor unit 1 includes an electronic component in a case, measuresan air pressure of the tire and an internal temperature thereof, andtransmits the measurement results to the outside of the tire. The base11 includes at least a pair of locking parts 13 and 13 which areprotruded from a bottom part 12. These locking parts 13 and 13 lock thesensor unit 1 by sandwiching the unit. The bottom part 12 of the base 11is fixed to an outer peripheral surface of the rim R, for example.Specifically, the sensor unit 1 is attachable to and detachable from thebase 11 fixed to the outer peripheral surface of the rim R.

In the above-described sensor system for a tire, a pair of contactpoints 14 and 14 are provided at portions of the base 11 where the basecomes into contact with the sensor unit 1. Moreover, in the base 11, aconductive path 15 is formed, which electrically connects the pair ofcontact points 14 and 14 to each other. Meanwhile, a pair of contactpoints 2 and 2 are provided at portions of the sensor unit 1 where theunit comes into contact with the base 11. Moreover, in the sensor unit1, a detection circuit 3 is formed, which electrically connects the pairof contact points 2 and 2 to each other. This detection circuit 3 isformed in the electronic component of the sensor unit 1.

In the thus configured sensor system for a tire, when the sensor unit 1is attached to the base 11, the detection circuit 3 is set in a closedstate. On the other hand, if the sensor unit 1 becomes detached from thebase 11 or moves out from a predetermined locking position on the base11 in assembly of the rim and the like, the detection circuit 3 is setin an open state. Therefore, based on the open or closed state of thedetection circuit 3, a relative change in a distance between the sensorunit 1 and a position where the sensor unit should be installed isdetected. Thus, an installation condition of the sensor unit 1 can beknown.

FIG. 2 shows a sensor system for a tire according to a second embodimentof the present invention. In FIG. 2, R denotes a rim, T denotes a tire,and S denotes a tire's air chamber. The sensor system for a tire of thisembodiment includes a sensor unit 21 for detecting information insidethe tire. The sensor unit 21 is installed in the tire's air chamber. Thesensor unit 21 includes an electronic component in a case, measures anair pressure of the tire and an internal temperature thereof, andtransmits the measurement results to the outside of the tire.

In the above-described sensor system for a tire, an eddy-current typeproximity sensor 22 which reacts to metal is provided in the sensor unit21. This proximity sensor 22 is disposed so as to face a position wherethe sensor unit 21 is installed, and generates an output according to amass of and a distance from a metal member existing in the position. Forexample, if the sensor unit 21 is attached to an outer peripheralsurface of the rim R, the proximity sensor 22 can be configured asdescribed below. Sensitivity of the proximity sensor 22 is controlled soas to react to the rim R made of metal, and, when the proximity sensor22 comes off the rim R, the sensor no longer reacts to the rim.Moreover, if the sensor unit 21 is attached to an inner surface of thetire, the proximity sensor 22 can be also configured as described below.The sensitivity of the proximity sensor 22 is controlled so as to reactto a steel wire embedded inside the tire, and, when the proximity sensor22 comes off the tire, the sensor no longer reacts to the steel wire. Inother words, the proximity sensor 22 is used as a switch. Alternatively,an output of the proximity sensor 22 when the sensor unit 21 isinstalled in a normal position is stored, and a relative change in adistance between the sensor unit 21 and its installation position may bedetected based on a change in the output.

In the thus configured sensor system for a tire, when the sensor unit 21is installed in a predetermined position, the proximity sensor 22generates a predetermined output. Meanwhile, if the sensor unit 21becomes detached from its installation position in assembly of the rimand the like, the output of the proximity sensor 22 changes. Therefore,the relative change in the distance between the sensor unit 21 and itsinstallation position is detected based on the output of the proximitysensor 22. Thus, an installation condition of the sensor unit 21 can beknown.

FIG. 3 shows a sensor system for a tire according to a third embodimentof the present invention. In FIG. 3, R denotes a rim, T denotes a tire,and S denotes a tire's air chamber. The sensor system for a tire of thisembodiment includes a sensor unit 31 for detecting information insidethe tire. The sensor unit 31 is installed in the tire's air chamber. Thesensor unit 31 includes an electronic component in a case, measures anair pressure of the tire and an internal temperature thereof, andtransmits the measurement results to the outside of the tire.

In the above-described sensor system for a tire, a rod-like probingmember 32 which is elastically energized toward an installation positionof the sensor unit 31 is provided in the sensor unit 31. Specifically,the probing member 32 can freely come out of or get back into the sensorunit 31 while being energized by an elastic body 33 such as a spring.The sensor unit 31 is installed in a state where the probing member 32pressed against the installation position is housed in the sensor unit31. Moreover, in the electronic component of the sensor unit 31, acircuit which is opened or closed according to a position of the probingmember 32 is provided.

In the thus configured sensor system for a tire, when the sensor unit 31is installed in a predetermined position, the probing member 32 is setin a state of being housed in the sensor unit 31. Meanwhile, if thesensor unit 31 becomes detached from its installation position inassembly of the rim and the like, the probing member 32 comes out of thesensor unit 31, and a relative position of the probing member 32 in thesensor unit 31 is changed. Therefore, a relative change in a distancebetween the sensor unit 31 and its installation position is detectedbased on displacement of the probing member 32. Thus, an installationcondition of the sensor unit 31 can be known.

In the first to third embodiments described above, the installationcondition of the sensor unit may be constantly monitored. In such acase, however, too much power is consumed. Thus, it is preferable thatdetecting means for detecting the relative change in the distancebetween the sensor unit and its installation position be operated atpredetermined time intervals.

A detection result concerning the installation condition of the sensorunit may be transmitted to the outside of the tire by utilizing atransmitter that is included in the electronic component of the sensorunit. In this event, in order to transmit information that the sensorunit is displaced from a predetermined installation position, a code forthe predetermined position in a communication protocol may be changed ora protocol signal different from a usual one may be transmitted.

FIG. 4 shows a sensor system for a tire according to a fourth embodimentof the present invention. In FIG. 4, R denotes a rim, T denotes a tire,and S denotes a tire's air chamber. The sensor system for a tire of thisembodiment includes a sensor unit 41 for detecting information insidethe tire. The sensor unit 41 is installed in the tire's air chamber. Thesensor unit 41 includes an electronic component in a case, measures anair pressure of the tire and an internal temperature thereof, andtransmits the measurement results to the outside of the tire.

In the above-described sensor system for a tire, the sensor unit 41includes a passive transponder 42. This passive transponder 42 transmitsa response signal in response to an inquiry signal from the outside ofthe tire. The passive transponder 42 may be inserted into the case ofthe sensor unit 41 as an independent component or may be included in acircuit of the electronic component of the sensor unit 41.

Moreover, in the above-described sensor system for a tire, a reader(scanner) 43 for providing the inquiry signal is simultaneously used.This reader 43 has a limited output. Specifically, an output range ofthe reader 43 is limited within a 10-cm radius, preferably within a 5-cmradius. Accordingly, if the passive transponder 42 is out of the outputrange of the reader 43, the response signal cannot be obtained for theinquiry signal.

In the thus configured sensor system for a tire, the sensor unit 41 isinstalled in a predetermined position on an inner surface of the tire T.For example, the sensor unit 41 is installed behind a specific characterdisplayed on a side face of the tire on an outer side of a vehicle.Accordingly, in a state where the rim is assembled, the reader 43 isbrought close to a position where the sensor unit 41 should be installedfrom the outside of the tire. Thus, the inquiry signal is provided. Inthis event, the response signal can be obtained if the sensor unit 41 isinstalled in the predetermined position. The response signal cannot beobtained, however, if the sensor unit 41 does not exist in thepredetermined position. Therefore, a relative change in a distancebetween the sensor unit 41 and its installation position is detectedbased on a response of the passive transponder 42 to the reader 43having the limited output. Thus, an installation condition of the sensorunit 41 can be known.

Although the embodiments of the present invention have been described indetail above, it should be understood that various changes,alternatives, and substitutions can be made without departing from thespirit and scope of the present invention, which are defined by theattached claims.

INDUSTRIAL APPLICABILITY

The present invention can be effectively utilized in tire manufacturingindustries and thus in automobile manufacturing industries.

1. A sensor system for a tire, in which a sensor unit is installed in atire's air chamber, comprising: detecting means for detecting a relativechange in a distance between the sensor unit and a position where thesensor unit is installed.
 2. A sensor system for a tire, in which asensor unit is installed in a tire's air chamber, comprising: a basewhich fixes the sensor unit in its installation position, the base beingattached to the sensor unit; a conductive path with a pair of contactpoints formed in the base, the conductive path connecting the contactpoints thereof; and a detection circuit with a pair of contact pointsformed in the sensor unit, the detection circuit connecting the contactpoints thereof, and the contact points being arranged corresponding topositions of the contact points in the base, wherein a relative changein a distance between the sensor unit and its installation position isdetected based on an open and closed state of the detection circuit. 3.A sensor system for a tire, in which a sensor unit is installed in atire's air chamber, comprising: a proximity sensor which reacts tometal, the proximity sensor being arranged in the sensor unit, wherein arelative change in a distance between the sensor unit and itsinstallation position is detected based on an output of the proximitysensor.
 4. A sensor system for a tire, in which a sensor unit isinstalled in a tire's air chamber, comprising: a probing member which iselastically energized toward an installation position of the sensorunit, the probing member being arranged in the sensor unit, wherein arelative change in a distance between the sensor unit and itsinstallation position is detected based on displacement of the probingmember.
 5. A sensor system for a tire, in which a sensor unit isinstalled in a tire's air chamber, comprising: a passive transpondermounted in the sensor unit, wherein a relative change in a distancebetween the sensor unit and its installation position is detected basedon a response of the passive transponder to a reader having a limitedoutput.